Nam Jong-Hoon, Cotton John R, Grant Wally
Department of Engineering Science and Mechanics, School of Biomedical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
Biophys J. 2007 Mar 15;92(6):1929-37. doi: 10.1529/biophysj.106.085092. Epub 2007 Jan 5.
The virtual hair cell we have proposed utilizes a set of parameters related to its mechanoelectric transduction. In this work, we observed the effect of such channel gating parameters as the gating threshold, critical tension, resting tension, and Ca(2+) concentration. The gating threshold is the difference between the resting and channel opening tension exerted by the tip link assembly on the channel. The critical tension is the tension in the tip link assembly over which the channel cannot close despite Ca(2+) binding. Our results show that 1), the gating threshold dominated the initial sensitivity of the hair cell; 2), the critical tension minimally affects the peak response, (I), but considerably affects the time course of response, I(t), and the force-displacement, F-X, relationship; and 3), higher intracellular [Ca(2+)] resulted in a smaller fast adaptation time constant. Based on the simulation results we suggest a role of the resting tension: to help overcome the viscous drag of the hair bundle during the oscillatory movement of the bundle. Also we observed the three-dimensional bundle effect on the hair cell response by varying the number of cilia forced. These varying forcing conditions affected the hair cell response.
我们提出的虚拟毛细胞利用了一组与其机电转换相关的参数。在这项工作中,我们观察了诸如门控阈值、临界张力、静息张力和Ca(2+)浓度等通道门控参数的影响。门控阈值是纤毛顶端连接组件施加在通道上的静息张力与通道开放张力之间的差值。临界张力是纤毛顶端连接组件中的张力,超过该张力,即使Ca(2+)结合,通道也无法关闭。我们的结果表明:1)门控阈值主导了毛细胞的初始敏感性;2)临界张力对峰值响应(I)影响最小,但对响应的时间进程I(t)和力-位移F-X关系有相当大的影响;3)较高的细胞内[Ca(2+)]导致较小的快速适应时间常数。基于模拟结果,我们提出了静息张力的作用:在毛束的振荡运动过程中帮助克服毛束的粘性阻力。我们还通过改变受迫纤毛的数量观察了三维束对毛细胞响应的影响。这些不同的受迫条件影响了毛细胞的响应。